Classification of Metal Removal Processes and Machine tools Introduction to Manufacturing and Machining Production Engineering covers two domains: (a) Production or Manufacturing Processes (b) Production Management (a) Manufacturing Processes This refers to science and technology of manufacturing products effectively, efficiently, economically and environment-friendly through Application of any existing manufacturing process and system Proper selection of input materials, tools, machines and environments. Improvement of the existing materials and processes Development of new materials, systems, processes and techniques All such manufacturing processes, systems, techniques have to be Technologically acceptable Technically feasible Economically viable and Eco-friendly Manufacturing Science and technology are growing exponentially to meet the growing demands for; (i) Increase and maintenance of productivity, quality and economy especially in respect of liberalization and global competitiveness (ii) Making micro and ultra-precision components for the modern electronics, computers and medical applications (iii) Processing exotic materials, coming up with rapid and vast advent of science and technology like aerospace and nuclear engineering. (b) Production Management This mainly refers to planning, coordination and control of the entire manufacturing in most profitable way with maximum satisfaction to the 1
customers by best utilization of the available resources like man, machine, materials and money. It may be possible to manufacture a product of given material and desired configuration by several processes or routes as indicated in Fig. 1. Fig. 1. Process convert input to output The various process routes may be different in respect of principle, technique, quality of products and time requirement and cost of manufacture. The best one is to be selected based on some criteria. Achieving the goal in manufacturing requires fulfillment of one or more of the following objectives: Reduction of manufacturing time Increase of productivity Reduction of manufacturing cost Increase in profit or profit rate The most significant and ultimate objective, i.e., Increase in Profit, Pr, can be attained by (i) Reducing the overall manufacturing cost, C m (ii) Increase in revenue, R by increasing quality and reliability of the products (iii) Enhancement of saleable production 2
Classification of Engineering Manufacturing Processes. It is difficult to tell the exact number of various manufacturing processes existing and are being practiced presently because a large number of processes have been developed until now and the number is still increasing with the growing demands and rapid progress in science and technology. All manufacturing processes can be classified in four major groups: (a) Shaping or forming Manufacturing a solid product of definite size and shape from a given material taken in three possible states: In solid state e.g., forging rolling, extrusion, drawing etc. In liquid or semi-liquid state e.g., casting, injection molding etc. In powder form e.g., powder metallurgical process. (b) Joining process Welding, brazing, soldering etc. (c) Removal process Traditional machining processes including turning, boring, drilling, reaming, threading, milling, shaping, planning, and broaching, as well as abrasive processes such as grinding, ultrasonic machining, lapping, and honing. Non-traditional machining processes including electrical and chemical means of material removal, as well as the use of abrasive jets, water jets, laser beams, and electron beams. (d) Regenerative manufacturing Production of solid products in layer by layer from raw materials in different form: Liquid e.g., stereo lithography Powder e.g., selective sintering Sheet e.g., LOM (laminated object manufacturing) Wire e.g., FDM. (Fused Deposition Modelling) 3
Regenerative Manufacturing is generally accomplished very rapidly and quite accurately using CAD and CAM for Rapid Prototyping and Tooling. Machining Purpose, Principle and Definition (a) Definition of Machining: Machining is an essential process of finishing by which jobs are produced to the desired dimensions and surface finish by gradually removing the excess material from the preformed blank in the form of chips with the help of cutting tool(s) moved past the work surface(s). Machining using cutting tools to remove some amount of a piece of material (metal, wood, plastics, ceramic, etc.) to precisely shape it for an intended use. This use of the physical action of cutting tools is also known as subtractive manufacturing. The primary machines used in machining are the engine lathe (metal lathe), milling machine (both horizontal and, most typically, vertical), drill press, and abrasive grinders. These and other machines can be either manual or automated. Most automated machines have CNC (computer numerical control) and are capable of producing very precise and complex parts with a high degree of repeatable accuracy for any number of applications. (b) Purpose of Machining Most of the engineering components such as gears, bearings, clutches, tools, screws and nuts etc. need dimensional and form accuracy and good surface finish for serving their purposes. Preforming like casting, forging etc. generally cannot provide the desired accuracy and finish. Machining to high accuracy and finish essentially enables a product fulfill its functional requirements improve its performance prolong its service 4
(c) Principle of Machining The basic principle of machining is typically illustrated in Fig. 2 Fig. 2 Principle of machining (turning) A metal rod of irregular shape, size and surface is converted into a finished rod of desired dimension and surface by machining by proper relative motions of the tool-work pair. (d) Machining requirements The essential basic requirements for machining work are shown in Fig. 3. Fig. 3. Requirements for machining 5
The blank and the cutting tool are properly mounted (in fixtures) and moved in a powerful device called machine tool enabling gradual removal of layer of material from the work surface resulting in its desired dimensions and surface finish. Additionally some environment called cutting fluid is used to ease machining by cooling and lubrication. (e) Machine Tool - definition and its function A machine tool is a non-portable power operated and valued device or system of devices in which energy is expended to produce jobs of desired size, shape and surface finish by removing excess material from the preformed blanks in the form of chips with the help of cutting tools moved past the work surface(s). Machine Tools produce geometrical surfaces like flat, cylindrical or any contour on the preformed blanks by machining work with the help of cutting tools. The physical functions of a Machine Tool in machining are: Firmly holding the blank and the tool Transmit motions to the tool and the blank Provide power to the tool-work pair for the machining action. Control of the machining parameters, i.e., speed, feed and depth of cut. Basic Mechanics of Metal Cutting The basic mechanics of chip-type machining processes are shown in Fig. 4. Fig. 4 Examples of chip-type machining operations. 6